Elevator Safety Systems

ABSTRACT

An elevator system comprising a hoistway ( 4 ) and an elevator car ( 2 ) arranged to travel vertically within the hoistway, the hoistway is provided with a sensing arrangement such as an infra-red curtain ( 10,12 ) for detecting the presence of a person on top of the car as the car approaches the top of the hoistway ( 8 ). The elevator system is arranged to limit further upward movement of the car in the event that a person is detected.

This invention relates to enhancements in the safety of elevators,particularly the detection of the unauthorised presence of a person ontop of an elevator car.

It is becoming increasingly common in elevator installations to providevery little space above the ordinary travel of the elevator car as thisreduces building costs and increases the available flexibility inbuilding design. However, there is a risk of injury in low overheadelevator installations as there is less refuge space for a person ridingon top of the elevator car as the car approaches the uppermost landing.It is therefore necessary to provide a series of safety systems such asa retractable balustrade and a special inspection mode for the elevatorcontroller which prevent the car from travelling to the top of thehoistway. These permit authorised inspections to be carried out safelyby an engineer riding on top of the car. However, if these safetymeasures are not all properly employed or are inadvertently ordeliberately overridden, there is an increased risk of injury. Thiscould result from an engineer not adhering to an approved procedure forcarrying out inspection or could result from an unauthorised persongaining access to the top of the car.

In view of the above, it is desirable automatically to prevent theelevator car moving to the uppermost end of its travel if a person ispresent on top of the car.

When viewed from a first aspect the present invention provides anelevator system comprising a hoistway and an elevator car arranged totravel vertically within the hoistway, the hoistway being furtherprovided with a sensing arrangement for detecting the presence of aperson on top of the car as the car approaches the top of the hoistway,the elevator system being arranged so as to limit further upwardmovement of the car in the event that a person is detected.

When viewed from a second aspect the invention provides a method ofpreventing injury to a person riding on top of an elevator car in alow-overhead elevator system the method comprising detecting thepresence of a person on top of the car as the car approaches the top ofa hoistway using means provided in the hoistway and limiting furtherupward movement of the car in the event that a person is detected.

Thus it will be seen by those skilled in the art, that in accordancewith the invention a person at risk of being injured at the top of thehoistway as the elevator car moves up will be detected and the elevatorsystem will limit upward movement of the car to reduce the risk ofinjury to that person.

The means for detecting a person on top of the car could be one that isable to distinguish between a living person and an inanimate object sothat it does not sense the presence of the car itself during normaloperation. For example, the sensing arrangement could comprise a passiveinfrared sensor for sensing the body heat of the person on top of thecar. Preferably, however, the sensing arrangement is adapted to detectthe presence of an object at the relevant vertical point of thehoistway.

A point in the hoistway above the normal travel of the elevator could bechosen but in very low overhead installations this may not givesufficient distance in which to stop the car safely without causinginjury to the person on top of it. In accordance with preferredembodiments therefore the sensing point is within the normal travel ofthe car and the elevator system is arranged to be able to distinguishbetween a person riding on top of the car and the car itself havingtraveled to the vertical sensing point during normal operation. Whilstthere are many ways of achieving this, it is preferred to use anexisting position reference system to determine the position of the carand to limit upward movement of the car in accordance with the inventiononly if it is determined via the position reference system that theelevator car is not intended to be in a position where it will bedetected by the sensing arrangement. One way of doing this would be forthe sensing arrangement to send a signal to the elevator controller andfor the elevator controller to be arranged to limit upward movement ofthe car based on the signals from the sensing arrangement and theposition reference system.

Alternatively, the sensing arrangement may be enabled when the elevatorcar is towards the top of the hoistway but still low enough that thereis sufficient space between the top of the car and the top of thehoistway to accommodate a person. For example, the sensing arrangementcould be activated when the elevator car is at the landing below theuppermost landing. By positioning the sensing arrangement above theposition of the elevator car when the sensing arrangement is activated,the sensing arrangement will only detect an object on top of the carrather than the car itself. Of course, if the position of the sensingarrangement is such that it will be passed by the elevator car duringnormal operation, this should not set off the safety system to limitmovement of the car. One possibility would be for a second positionsignal to be used to deactivate the sensor. Alternatively the sensingarrangement could be enabled when the elevator car is above thepenultimate landing a time measurement made to determine whether anobject is detected before it would be expected for the car itself to bedetected.

Upon detection of an unauthorised person on top of the car there are anumber of possibilities for taking action to prevent injury to thatperson. For example the elevator controller may immediately prevent anyfurther upward movement of the car by interrupting power to the elevatormotor and applying the brake. Additionally, or alternatively, a physicalsafety device may be automatically employed.

In a preferred set of embodiments the sensing arrangement comprisesmeans for emitting a sensing radiation and means for detecting theemitted radiation so as to enable the presence of an object in the pathof the radiation to be detected. The sensing arrangement could be suchthat radiation reflected from the detected body is sensed but preferablythe arrangement is such that the radiation travels across the hoistwayto be detected so that the presence of a body at that vertical point inthe hoistway interrupts the sensing of the radiation. Most preferablythe sensing arrangement comprises a plurality of beams spanning thehoistway and one or more sensors arranged to detect said beam(s).

The radiation employed may be of any convenient nature such asultrasound, microwave or visible light but preferably infrared radiationis employed since the associated sensors and emitters are relativelyeasily available and inexpensive whilst being reliable.

A preferred embodiment of the present invention will now be described,by way of example only with reference to the accompanying drawings inwhich:

FIG. 1 is a front view of a low overhead elevator hoistway showing thedanger posed to persons on top of the car;

FIGS. 2 a and 2 b are front and perspective views respectively of anelevator system embodying the invention showing activation of theinfrared curtain;

FIGS. 3 a and 3 b are front and perspective views respectively showingdetection of an unauthorised person on top of the car; and

FIG. 4 is a front view of the embodiment of FIGS. 2 and 3 where the caris safely stopped to prevent injury to the person on top of the car.

FIG. 1 shows an elevator car 2 which is arranged to move verticallywithin a hoistway 4. It will be seen that when the car 2 is adjacent theuppermost landing 6 there is very little space 7 between the top of thecar 2 and the ceiling 8 of the hoistway. In particular, there is norefuge space for a person who happens to be on top of the car.

In low overhead systems such as that shown, a series of safety measuresis required to ensure that the car cannot reach the uppermost landing 6with someone riding on top of it. Normally such systems are linked tocertain conditions like putting the elevator in a special inspectionmode or the detection of unauthorised opening of a hoistway doorindicating access to the top of the car by an unauthorised person.

However, it is not impossible that detection elements can be overriddenor the elevator not properly put into inspection mode. Specifically, adoor detection system can be overridden by an unauthorised user who canthen ride on top of the car in normal mode. As will be seen from FIG. 1,this is extremely dangerous and potentially fatal. This may be preventedin accordance with the invention as will now be described with referenceto FIGS. 2 to 5.

According to the embodiment of the invention described herein, in theuppermost part of the hoistway 2 there is provided an infrared sensorand emitter arrangement comprising an elongate emitter array 10 and acorresponding elongate sensor array 12 disposed horizontally within theelevator shaft by being attached to the respective guide rails 14. Inthe embodiment shown in the Figures the emitter array 10 comprises aplurality of separate emitters which emit-infrared beams spanning thehoistway at a number of different angles to be sensed by a correspondingplurality of sensors at the sensor array 12 on the other side of thehoistway. By having a plurality of independent emitters and sensors theprobability of spurious detection e.g. from small pieces of debris orflying insects in the hoistway may be reduced. However, it is envisagedthat a single beam could be employed which could span the hoistway justonce or alternatively which could be reflected one or more times toprovide a greater spatial extent.

It will be seen that the sensor and emitter arrays 10,12 are providedapproximately one third of the way up the uppermost landing space 6. Thesensing arrangement 10,12 is activated when the elevator car 2 isadjacent the landing 16 below the uppermost landing 6. As will be seennow with reference to FIGS. 3A and 3B, as the elevator car moves upbeyond the penultimate landing 16 the unauthorised person 18 on top ofthe car will break the infrared beam between the emitter array 10 andthe sensor array 12 which will be detected by the sensor array 12 as aninterruption to its signal. Once this has been detected, further upwardmovement of the elevator car 2 will be prevented and the brake will beapplied. As may be seen in FIG. 2A, this means that enough space remainsabove the top of the car 2 to prevent injury to the unauthorised person18 on top of the car. The system could be arranged so as to require amanual reset e.g. by an authorised engineer before it may recommencenormal operation although this is not essential.

If there is no unauthorised person on top of the car, the top of the caritself will eventually break the beam between the emitter array 10 andsensor array 12 as the car moves up to the uppermost landing 6. However,this does not lead to suspension of operation of the car since theposition reference system (PRS) signal indicates that the car isexpected to be at a position such that it breaks the beam.

It will be appreciated by those skilled in the art that variations andmodifications to the described embodiment may be made without departingfrom the scope of the invention. For example, other means for sensingthe presence of a person on top of the car may be provided such asvisible light, ultrasonic, microwave or other sensors. Moreover timingsignals could be used rather than position signals to distinguishbetween the car and an unauthorised person on top of it.

1. An elevator system comprising a hoistway (4) and an elevator car (2)arranged to travel vertically within the hoistway, the hoistway beingfurther provided with a sensing arrangement (10,12) for detecting thepresence of a person on top of the car as the car approaches the top ofthe hoistway (8), the elevator system being arranged so as to limitfurther upward movement of the car in the event that a person isdetected.
 2. An elevator system as claimed in claim 1 wherein thesensing arrangement (10,12) is adapted to detect the presence of anobject at a predetermined vertical point of the hoistway.
 3. An elevatorsystem as claimed in claim 1 or 2 wherein said predetermined verticalpoint is within the normal travel of the elevator car (2), the elevatorsystem being arranged to be able to distinguish between a person ridingon top of the car and the car itself having travelled to said pointduring normal operation.
 4. An elevator system as claimed in claim 3arranged in use to use a position reference system to determine theposition of the car (2) and to limit upward movement of the car only ifit is determined via the position reference system that the elevator caris not intended to be in a position where it will be detected by thesensing arrangement (10,12).
 5. An elevator system as claimed in claim 4wherein said sensing arrangement (10,12) is arranged to send a signal toan elevator controller, the elevator controller being arranged to limitupward movement of the car (2) based on said signal and an output fromthe position reference system.
 6. An elevator system as claimed in claim4 wherein the sensing arrangement (10,12) is arranged so as to beenabled when the elevator car (2) is towards the top of the hoistway (4)but still low enough that there is sufficient space between the top ofthe car and the top of the hoistway to accommodate a person.
 7. Anelevator system as claimed in claim 6 arranged such that the sensingarrangement (10,12) is enabled in use when the elevator car is at alanding (16) below an uppermost landing (6).
 8. An elevator system asclaimed in any of claims 4 to 7 comprising means for generating aposition signal for disabling said sensing arrangement (10,12) as thesensing arrangement is approached by the car (2).
 9. An elevator systemas claimed in any of claims 4 to 7 comprising means for making a timemeasurement when the car (2) has passed a predetermined point, saidelevator system being arranged to limit movement of the car if thesensing arrangement (10,12) detects an object before it would beexpected for the car itself to be detected.
 10. An elevator system asclaimed in any preceding claim comprising means for immediatelypreventing any further upward movement of the car (2) upon detection ofan unauthorised person on top of the car.
 11. An elevator system asclaimed in any preceding claim comprising means for automaticallyemploying a physical safety device upon detection of an unauthorisedperson on top of the car (2).
 12. An elevator system as claimed in anypreceding claim wherein the sensing arrangement comprises means foremitting a sensing radiation (10) and means for detecting the emittedradiation (12) so as to enable the presence of an object in the path ofthe radiation to be detected.
 13. An elevator system as claimed in claim12 wherein the sensing arrangement (10,12) is such that the radiationtravels substantially horizontally across the hoistway (4).
 14. Anelevator system as claimed in claim 12 or 13 wherein the sensingarrangement (10,12) comprises a plurality of beams spanning the hoistwayand one or more sensors (12) arranged to detect said beam(s).
 15. Anelevator system as claimed in claim 12, 13 or 14 wherein said radiationis substantially infrared radiation.
 16. A method of preventing injuryto a person riding on top of an elevator car (2) in a low-overheadelevator system the method comprising detecting the presence of a personon top of the car as the car approaches the top of a hoistway (8) usingmeans (10,12) provided in the hoistway and limiting further upwardmovement of the car in the event that a person is detected.
 17. A methodas claimed in claim 16 comprising detecting the presence of an object ata predetermined vertical point of the hoistway (4).
 18. A method asclaimed in claim 16 or 17 comprising distinguishing between a personriding on top of the car (2) and the car itself.
 19. A method as claimedin claim 18 comprising using a position reference system to determinethe position of the car (2) and limiting upward movement of the car onlyif it is determined via the position reference system that the elevatorcar is not intended to be in a position where it will be detected by thesensing arrangement (10,12).
 20. A method as claimed in claim 19comprising sending a signal to an elevator controller, the elevatorcontroller limiting upward movement of the car (2) based on said signaland an output from the position reference system.
 21. A method asclaimed in claim 19 comprising enabling the sensing arrangement (10,12)when the elevator car (2) is towards the top of the hoistway (4) butstill low enough that there is sufficient space between the top of thecar and the top of the hoistway to accommodate a person.
 22. A method asclaimed in claim 21 comprising enabling the sensing arrangement (10,12)when the elevator car (2) is at a landing (16) below an uppermostlanding (6).
 23. A method as claimed in any of claims 19 to 22comprising generating a position signal for disabling said sensingarrangement (10,12) as the sensing arrangement is approached by the car(2).
 24. An elevator system as claimed in any of claims 19 to 22comprising making a time measurement when the car (2) has passed apredetermined point and limiting movement of the car if the sensingarrangement (10,12) detects an object before it would be expected forthe car itself to be detected.
 25. A method as claimed in any of claims16 to 24 comprising immediately preventing any further upward movementof the car (2) upon detection of an unauthorised person on top of thecar.
 26. A method as claimed in any of claims 16 to 25 comprisingautomatically employing a physical safety device upon detection of anunauthorised person on top of the car (2).
 27. A method as claimed inany of claims 16 to 24 comprising emitting a sensing radiation anddetecting the emitted radiation thereby to detect the presence of anobject in the path of the radiation.